Display the timestamp and the time delta spent between
messages. If used together with --notime then only the time delta
without the timestamp is printed.

-E, --console-on

Enable printing messages to the console.

-e, --reltime

Display the local time and the delta in human-readable
format. Be aware that conversion to the local time could be inaccurate
(see -T for more details).

-F, --file file

Read the syslog messages from the given file. Note
that -F does not support messages in kmsg format. The old syslog
format is supported only.

-f, --facility list

Restrict output to the given (comma-separated) list
of facilities. For example:

dmesg --facility=daemon

will print messages from system daemons only. For all
supported facilities see the --help output.

-H, --human

Enable human-readable output. See also --color,
--reltime and --nopager.

-k, --kernel

Print kernel messages.

-L, --color[=when]

Colorize the output. The optional argument when can
be auto, never or always. If the when argument
is omitted, it defaults to auto. The colors can be disabled; for
the current built-in default see the --help output. See also the
COLORS section below.

-l, --level list

Restrict output to the given (comma-separated) list
of levels. For example:

dmesg --level=err,warn

will print error and warning messages only. For all
supported levels see the --help output.

-n, --console-level level

Set the level at which printing of messages is done
to the console. The level is a level number or abbreviation of the
level name. For all supported levels see the --help output.

For example, -n 1 or -n alert prevents all messages, except
emergency (panic) messages, from appearing on the console. All levels of
messages are still written to /proc/kmsg, so syslogd(8) can
still be used to control exactly where kernel messages appear. When the
-n option is used, dmesg will not print or clear the
kernel ring buffer.

-P, --nopager

Do not pipe output into a pager. A pager is enabled by
default for --human output.

-r, --raw

Print the raw message buffer, i.e. do not strip the
log-level prefixes.

Note that the real raw format depends on the method how dmesg(1)
reads kernel messages. The /dev/kmsg device uses a different format than
syslog(2). For backward compatibility, dmesg(1) returns data
always in the syslog(2) format. It is possible to read the real raw
data from /dev/kmsg by, for example, the command 'dd if=/dev/kmsg
iflag=nonblock'.

-S, --syslog

Force dmesg to use the syslog(2) kernel
interface to read kernel messages. The default is to use /dev/kmsg rather
than syslog(2) since kernel 3.5.0.

-s, --buffer-size size

Use a buffer of size to query the kernel ring
buffer. This is 16392 by default. (The default kernel syslog buffer size
was 4096 at first, 8192 since 1.3.54, 16384 since 2.1.113.) If you have
set the kernel buffer to be larger than the default, then this option can
be used to view the entire buffer.

-T, --ctime

Print human-readable timestamps.

Be aware that the timestamp could be inaccurate! The
time source used for the logs is not updated after system
SUSPEND/RESUME.

-t, --notime

Do not print kernel's timestamps.

--time-formatformat

Print timestamps using the given format, which can
be ctime, reltime, delta or iso. The first
three formats are aliases of the time-format-specific options. The
iso format is a dmesg implementation of the ISO-8601
timestamp format. The purpose of this format is to make the comparing of
timestamps between two systems, and any other parsing, easy. The
definition of the iso timestamp is:
YYYY-MM-DD<T>HH:MM:SS,<microseconds><-+><timezone
offset from UTC>.

The iso format has the same issue as ctime:
the time may be inaccurate when a system is suspended and resumed.

-u, --userspace

Print userspace messages.

-w, --follow

Wait for new messages. This feature is supported only on
systems with a readable /dev/kmsg (since kernel 3.5.0).